1. Field of the Invention
The present invention relates to synchronous controller for synchronously operating a plurality of actuators.
2. Description of the Related Art
A block diagram and a timing chart showing an example of conventional synchronous control equipment connecting a command controller and an actuator controller with a general purpose bus are shown in FIG. 5 and FIG. 6. The set cycle value, the initial count value, the set cycle values 1 and 2, and the output cycle values 1 and 2 shown in the timing chart of FIG. 6 are predetermined values necessary for control of the synchronous control device. In this synchronous control equipment, counter 22 in main controller 4, counter 22a in actuator controller 2a, and counter 22b in actuator controller 2b are incremented by clock pulses output from a clock generator 14.
The procedure for performing synchronous actuator operation begins at timing t1 in the timing chart of FIG. 6. A signal is output from counter synchronous controller 43 to count setters 23a, 23b of actuator controllers 2a, 2b via IF converter 42 and exclusive IF 41. Counters 22a, 22b are reset to the initial count value by this signal. At this time, counter synchronous controller 43 also resets counter 22 in a similar way. Counters 22, 22a, and 22b arc set to the same value by this operation. In addition, because these counters 22, 22a, and 22b are incremented by the same clock pulses output from clock generator 14, the count values of these counters always coincide. At the same timing t1, action command controller 12 of main controller 4 successively outputs a command A for actuator controller 2a and a command B for actuator controller 2b, which are sent via general purpose bus Ifs 15 and 17, and IF converter 42.
At timing t2, action controller 21a receives action command A and begins to calculate action signal A' to be output to actuator 3a, taking into consideration signals such as position data and velocity data detected by detector 4a. Similarly, at timing t3, action controller 21b receives action command B and begins to calculate action signal B' to be output to actuator 3b, taking into consideration signals such as position data and velocity data detected by detector 4b. At timing t4, at which point counter 22a has reached output cycle value 1, action controller 21a outputs action signal A' calculated before to actuator 3a. At this time, counter 22b shows the same output cycle value 1 as counter 22a because both counters have been set at timing t1. At timing t4, action controller 21b outputs previously calculated action signal B' to actuator 3b in a similar manner as action controller 21a. At timing t10 in the timing chart of FIG. 6, at which counter 22 has reached set cycle value 1, action command controller 12 outputs action commands C and D, and action controllers 21a and 21b calculate action signals C' and D' to be output to actuators 3a and 3b. When counters 22a and 22b have reached output cycle value 2, action controller 21a outputs action signal C' calculated before to actuator 3a, and action controller 21b outputs action signal D' to actuator 3b. Similarly, after timing t20 in the timing chart of FIG. 6, at which counter 22 has reached set cycle value 2, action controllers 21a and 21b can periodically receive action commands because count values of counters 22, 22a, and 22b are the same, and further can periodically and simultaneously output action signals to actuators 3a and 3b. Thus, synchronous operation of the respective actuators become possible.
As described above, in conventional synchronous control equipment in which a command controller is connected to an actuator controller with a general purpose bus, high frequency clock pulses are supplied to a plurality of actuator controllers. Consequently, when a large number of actuator controllers are to be connected, waveform distortion due to increase of load capacity of clock pulses, reflection of signals, etc. are generated. This may then result in equipment error due to counter malfunction. In addition, because connection by a signal line having high driving ability is necessary for preventing the malfunction, connection by exclusive IF is required. Further, even in the case of the connection by exclusive IF, it is not easy to connect additional actuators because the number of connections is limited.